Electric-current rectifier



Nov.

S. RUBEN ELECTRIC CURRENT RECTIFIER Filed Sept, 22, 1924 fama/ql 13u/56721,.

Patented Nov. 15, 1927.

UNITED STATES PATENT OFFICE. y

SAMUELYRUBEN, F `NEW YORK, N. Y., ASSIGNOR, BY MESNE ASSIGNMENTS, T0 RUBEN RECTIFIER CORPORATION OF DELAWARE.

ELECTRIC-CURRENT RECTIFIER.

Application led September 22, 1924. Serial No. 739,188.

This invention relates to electrocurrent rectiiers and more particularly to an electrochemical rectifier of the dry contact-surface t pe.

yRectiiers of the above type are characterized by the use of an electrode of electropositive material such as aluminum connected in circuit with another electrode through an intermediate layer of a sulphur compound 1o and depend for their operation upon the presence of a current blocking or rectifying film of one of the electrodes.- Such rectifiers heretofore available have been loW in etliciency and limited in their usecto small currents, becoming unstable after a short period of use.

The invention has for vits object generally the provision of a rectifier of the dry surface Contact variety which is free from the limitations mentioned above and is capable of use over relatively long periods of time and has a sustained current output.

Other objects of the invention Will in part be obvious and Will in part appear hereinafter.

The invention accordingly comprises the features of construction, combinations of elements, and arrangement of parts, which Will be exemplified in the constructions hereinafter set forth and the scope of the application of which Will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention reference should be had to the following detailed description taken in connection with the accompanying drawing, in Whichz YFig. l is an axial, cross-sectional view of the invention embodied in the form of a cartridge fuse;

Fig. 2 is a circuit diagram showing the use of two of the rectifiers with a transformer and filter circuit for .utilizing both halves of the cycle;

Fig. 3 is a modified form for@ use with large currents;

Fig. 4; is a cross-sectional view of a series type in the form of a cartridge fuse with severa-l rectifier elements in series for relatively high voltages; and

Fig. 5 is a diagram illustrating the method of forming a coating on one of the electrodes.

Referring to the drawings and first to Fig. 1, an electrode l of an electro-positive material, preferably one of aluminum, having a coating of sulphide indicated at 2, is placed in contact With a second or electro-negative eltelnentdin the forn gf a plate or ldisk sown a an compose o cu ic sul i'de uS and having its oppositepfreplpaed iii con)- tact with another element 4, which is a good conductor of heat and electricity, for example, brass.` These constitute essential elements ofthe invention and may be given any physical form affording arrangement of the different contacting surfaces in the order shown. In the present form the elements 1, 3 and 4 are mounted Within a cylindrical casing 5 of insulating material, for example bakelite, threaded at its ends to take the threaded terminal plugs 6 of suitable conducting material such as brass or cop er, which through the interposed spring Was er 7 hold the elements in place and in contact under constant pressure, compensating for expansion and contraction of the parts due for example7 to temperature changes.

In accordance with the preferred form of the invention a specially prepared sulphide coating is used on the electro-positive or 80 aluminum electrode. In rectiers of the present general type heretofore proposed, it Was found that the variable contact resistance at the rectifying film is the fundamental factor Which prevents eflicient or practical operation. This variation in resistance at the rectifying film is due to the reaction which here takes place, namely, dry contact electrolysis, in Which' a film is formed by the passage of an inverse current through the contacting surfaces of aluminum and a sulphur bearing compound. The density of the film thus produced is limited for the reason that just as soon as a slight film is formed it serves to prevent the further 95 formation of film. Regardless of hoW high v an inverse potential is used in forming the lm, the initially formed film is accompanied by a resistance product which insulates and reduces the inverse film forming 100 current to such a low value that the film necessaryy to withstand continuous alternating current operation cannot thus be formed.

It has been found that a coating of aluminum sulphide having the desired density 105 may be formed on the aluminum electrode before assembling the elements by chemical process, and that the assembled rectifier unit With a coating formed iyill coact to impart substantially unilaterally conductive or recti- 110 fying properties without the necessity of irst passing an inverse current for any material forming period, its alternating current oper ation being substantially constant without sparking between the sulphide and the aluminum. The word density is here used, not in its restricted sense as meaning mass or specific gravity but, in a broad sense to indicate density, thickness or durability as to operating strength or resistance to over-load break-down.

A method of producing this dense and eiiicient resistance coating consists in subjecting the aluminum electrode to a bath of alkaline sulphide, such as sodium sulphide heated to about 100 C., the aluminum electrode bein made the anode in a current path throu h te sulphide solution to a suitable catho e electrode such as brass or nickle, which current is supplied from a suitable source with variable potential. The potential is increased with increasing strength or density of the coating up to a. voltage higher than that used in the application of the unit. A difference of potential of 35 volts will produce a coating of desired density. When the potential to be applied to the units is of low value, the electrolytic method of formation need not be used, since by boilin the aluminum electrodes in a concentrate solution of sodium sulphide, a coating of sufficient density is formed, or where only a slight coating is sufficient, heating is not required.

The arrangement of apparatus for carrying out the electrolytic process of forming the coating is indicated diagrammatically in Fig. 5 in which 8 indicates a vessel of suitable heatresisting and transparent material such as thin tempered glass for example, glass sold under the trade-name of pyrex, which vessel contains a concentrated solution of sodium sulphide in which the aluminum element 9 to be coated and a cathode element 10 of brass or copper are immersed. The aluminum electrodoe 9 is connected through the conductor 11, milliammeter 12 and conductor 13 to the positive terminal of a variable potential battery 14, while the anode element 10 is connected through conductor 15 to the variable contactor 16 adapted to engage different taps on the minus side of the battery 14. The purpose of the transparent container 8 is to enable the physical condition of the coating to be observed during the progress of the coating process, and the purpose of the milliammeter is to indicate the electrical characteristics of the film during the process, the potential bein applied until the meter indicates a negligi le current iiow.

By the process of coating just described a pure sulphide coating may not be produced; it ossibly contains more or less aluminum hydroxide. This however is not detrimental as it does not alter beyond operating limits the resistance value of the coating desired to be obtained.

By the present invention the electronegative electrode element is a good electrical conductor contain' g a sulphur component which 1s readily given up to the electro sitlve electrode element, here provided, w ereby the rectifying upon injury, is immediately and automaticall repaired by the reaction electro-chemica y produced at the junction of the electrode elements.

The electronegative electrode element is the intermediate element in the operative combination here shown, and is a disc having a composition adapted to yield sul hur in this manner. Cuprlc sulphide (Oud) is a suitable material for its composition. Its use in the electronegative electrode element is thus an important feature of the present invention, since it was found that a highly eiiicient and stable rectifier for use under practical conditions requiring a, wide margin of safety as to over-load, extended use, etc., which could not be produced with ordinary cuprous sulphide (CuzS) as the electronegative electrode cle ment. On the other hand, cupric sulphide (CnS) especially that produced by the method to be hereinafter described, has been found to have the necessary qualities to satisfy commercial requirements.

In order to produce electrode elements of cupric sulphide, which have the improved electrical characteristics aboveclescribed, a preferred method consists in'heating the copper in the form of a metallic copper plate of a thickness, preferably, of about 5 millimeters, in sulphur vapors in a non-oxidizing atmosphere at a temperature above 150 degrees centigrade, preferably about 45() degrees centigrade. Under this treatment substantially the entire copper plate becomes converted into a cupric sulphide plate, taking the form of a hard, darkblue to blackish, solid, metal-like material, having conducting and other electrical characteristics, for example, a sufficiently low resistance which make it much superior to cuprous sulphide, (hemisulphide) or ordinary cupric sulphide otherwise produced. In the method above described the thickness of the initial copper plate and the temperature at which it is exposed to the sulphur vapor, are important elements of the process. A temperature above the minimum specified is found to be necessary to insure the prevention of the formation of cuprous sulphide (CuS) and yieldsfhe necessary solid cupric sulphide u Using a pair of rectiers constructed as described in the combination and arrangement of circuits and ancillary apparatus indicated diagrammatically in Fig. 2, the constants were as follows:

(ifi

Area of rectifying film, 4 square square centimeters. v

Output Voltage of filter circuit, 6 volts.

Transformer ratio, step down, 10 to one.

Direct current resistance, in inverse connection, 1,0700V ohms.

Direct current resistance, in conductive connection, .5 ohms.

Referring to the circuit connections of Fig. 2 in detail, 20 is a step down transformer having its primary Winding 2l connected With a commercial source of alternating current 22, in the present instance a llO- volt electric light and power circuit, and its secondary winding 23, which is a split winding, connected through a filler circuit, consisting of the inductance 24 and condensers 25 and 25a with a pair of rectiiiers 26 and 27. The terminals of the condensers 25 and 25a are connected to the direct current output terminals 28 and 29 which in operation are connected or bridged by the desired direct current consumption device not shown. It will be seen that with the rectifying devices 26 and 27 connected to rectify in the direction indicated by the adjacent arrows, both sides of the cycle of the alternatingr currents induced in the winding 23 are rectified into unidirectional pulsating current which is smoothed out into a substantially uniform direct current by the action yof the inductance 24 and condenser 25.

In Fig. 3 is shown a form of the invention designed for commercial use where large current capacity is required. This consists essentially of the same elements as that of Fig. 1, but with greater contact or operating area and with means for facilitating the radiation of heat. More especially it comprises a central electrode 34 of copper, having both extended surfaces in contact with plates 33 of cuprc sulphide (CnS) which in turn have their outer or remote faces in contact with a pair of aluminum electrodes 31, the whole being clamped together by clamping bolts 36 and maintained under constant pressure by spring Washers 37. The inner or contacting surfaces of the aluminum electrodes 31 are provided with a coating of aluminum sulphide 32, while the outer faces are provided with fianges 3S to facilitate the radiation of heat. There the central electrode 34 passes out beyond the lower clamping bolt 36 it is perforated with an opening arranged to permit the bolt. to pass therethrough without touching. A binding post 39 is mounted on the central electrode for making circuit connections therewith, while connection may be made with aluminum electrodes through the lower bolt 36.

The arrangement of Fig. 4 is the same as that of Fig. l in all respects except that the group of elements l, 3 and 4 is repeated a number of times and the cylindrical casing 5 made suiciently long to accommodate the increased number of groups. This arrangement is intended for use in relatively high potential circuits such as the standard 110- volt circuit without the use of a step down transformer, the number of complete groups of elements varying according to the voltage. In all the various forms of the invention it is important "to have the contacting surfaces of the elements, especially the coated surface of the aluminum and the adjacent or complementary surface of the cupric sulphi e, ground to a uniform and polished surace.

While there is here shown and described certain specific embodiments of the inven tion, it is to be understood that the invention is not limited to such specific embodiments but contemplates all such variants and modifications as fairly fall within the scope of the appended claims. For example, the device may take any physical form, especially as to the arrangement of its terminals, enabling it to be readily substituted for other forms of current rectifiers, such as a two` electrode rectifier tube or a mercury* vapor tube, without disarrangement of the controlling circuits and ancillary apparatus, such as transformers, filter circuits and the like. Having described my invention, what I claim as new and desire to secure by Letters Patent is l. An electric cell of the dry surface contact variety adapted for the rectification of alternating currents and the like, comprising 100 electropositive and electronegative electrode elements relatively widely divergent in the electrochemical series and disposed to maintain a continuously formed current blocking film therebetween; said electronegative electrode element comprising cupric sulphide.

2. An electric cell of the dry surface contact Variety adapted for the rectification of alternating currents and the like, comprising electropositive and electronegative electrode elements relatively Widely divergent in the electrochemical series and disposed to maintain a continuously formed current blocking film therebetween; said electropositive electrode element comprising a body of aluminum, and said electronegative electrode element a body of cupio sulphide.

3. An electric cell of the dry surface contact variety adapted for the rectification of alternating currents and the like, comprising electropositive and electronegative electrode elements relatively widely divergent in the electrochemical series and disposed to maintain a continuously formed current blocking film therebetween; said electropositive electrode element comprising a body of sulphide coated metallic aluminum, and said electronegative electrode element a body of cupric sulphide.

4. An electric cell of the dry surface oontact variety adapted for the rectification of alternating currents and the like, comprising electropositive and electronegative electrode elements relatively widely divergent in'the electrochemical series and disposed to maintain a continuously'formed current blocking film therebetween; said electropositive electrode element comprising a body of metallic aluminum having a preformed resistance coating, and said electronegative electrode element being a metallic compound having a surface adapted to react with said coating for current rectification and containing cupric sulphide.

5. An electric cell of the dry surface contact variety adapted for the rectification of alternating currents and the like, comprising electropositive and electronegative electrode elements relatively widely divergent in the electrochemical series and disposed to maintain a continuously formed current blocking film therebetween; said electropositive electrode element comprising a body of metallic aluminum having a'preformed coating of aluminum sulphide, and said electronegative electrode element having a surface containing cupric sulphide adapted to react with the coating on said electropositive electrode element.

An electric current rectifying cell of the dry surface contact variety comprising an electropositive electrode element having a contacting surface of aluminum sulphide, and an electronegative electrode element of cupric sulphide; said electrode elements being disposed for the continuous maintenance of an interposed asymetric current blocking film.

7. An electric cell of the dry surface contact variety adapted for the rectification of alternating currents and the like, comprising electropositive and electronegative electrode elements relatively widely divergent in the electrochemical series and disposed vto maintain a continuously formed currentblocking film therebetween; said clectropositive electrode element comprising a body of an electropositive metal having a preformed coating on one surface of a com ound thereof, and said electronegative e ectrode element having a coacting surface comprising cupric sulphide adapted to react with the coating on said electropositive electrode element.

8. An electric cell of the dry surface contact variety, adapted for the rectification of alternating currents and the like, comprising electropositive and electronegative electrode elements which are relatively electropositive and electronegative with respect to each other, and disposed to maintain an inverse current-blocking film at their contacting surfaces; the electropositive electrode element being a metal having a preformed coating containlng a sulphide, the electronegative ellecrode element comprising cupric sulp n e.

9. An electric cell of the dry surface contact variety, adapted for the rectification of alternating currents and the like, comprising electropositive and electronegative electrode elements which are relatively electropositive and electronegative with respect to each other, and disposed to maintain an inverse current-blocking film at their Contact ing surfaces; the electropositive electrode element being a metal having a preformed coating containing a compound thereof, the electronegative electrode element comprising a maximum valent compound of copper with sulphur whereby it is adapted to yield sulphur electrochemically to said film upon the passage of inverse current.

10. An electric cell of the dry surface contact variety, adapted for the rectification of alternating currents and the like, comprising electropositive and electronegative electrode elements which are relatively .electropositive and electronegative with respect to each other, and disposed to maintain an inverse current-blocking film at their contacting surfaces; the electropositive electrode element being aluminum having a preformed coating containing a compound thereof, the electronegative electrode element comprising at maximum valent compound of copper with sulphur whereby it is adapted to yield sulphur electrochemically to said film upon the passage of inverse current.

In testimony whereof I hereunto afiix my signature.

SAMUEL RUBEN. 

